Avalanche Forecast

Issued: Feb 29th, 2012 9:15AM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Wind Slabs and Persistent Slabs.

Avalanche Canada swerner, Avalanche Canada

The snowpack is tricky to predict at the moment. Backcountry travel requires local knowledge, extensive experience and training. Please read the new Forecaster's Blog Post.

Summary

Confidence

Good

Weather Forecast

Thursday: Fairly benign, resulting in dry, cold conditions, with sunny breaks. Ridgetop winds light from the NW. Treeline temperatures near -8. Freezing levels at valley bottom. Friday: A series of systems will arrive, light snowfall amounts early Friday morning. Then moderate amounts could accumulate 15-25 cm during the day. Ridetop winds will be strong from the SW. Freezing levels near 600 m. Saturday: Heavy snow amounts. Ridgetop winds moderate-strong from the WSW. Freezing levels may rise to 1000 m by the afternoon.

Avalanche Summary

Natural avalanche activity reports have tapered off. Sluffing is seen out of steep terrain, and small slabs rider triggered from convexities. On Tuesday extensive avalanche control work with the use of explosives was completed. Results included 1 size 3, @ 1320 m , on an East aspect, and numerous size 1-2 on East aspects between 12-1300 m. I suspect that conditions may still be ripe for rider triggers; especially wind loaded pockets and sheltered areas where buried SH layers may still linger. The snowpack is very tricky at the moment. Backcountry travel requires local knowledge, extensive experience and training. The obvious clues that show snowpack instability may not be there. You need to dig deep, do your detective work and make good decisions

Snowpack Summary

Due to changing winds, wind slabs can be found on N-NE aspects and S-SW aspects in the alpine on exposed slopes at treeline. Currently, up to 60cm of snow sits over the mid February interface. This interface is variable, it consists of a strong melt freeze crust below 1000m, above 1000 m exists facets, surface hoar (in more sheltered areas), sun crust or wind press. The surface hoar is not widespread but is responsible for much of the larger avalanches that occurred earlier this week. This layer should be on your radar, as it's susceptible to rider triggers. With forecast wind, snow and rising freezing levels this layer may show its wrath again. It's a good time to play conservatively. Below this, the mid and lower snowpack is well settled and strong.

Problems

Wind Slabs

An icon showing Wind Slabs
Moderate winds and new snowfall have created new and reactive wind slabs on lee terrain. Recent outflow winds have compounded this problem with reverse loading.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The persistent interface from mid February remains a concern. Large avalanches occurred earlier in the week, with these layers being suspect.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 6

Valid until: Mar 1st, 2012 8:00AM

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